Pumping apparatus for a vehicle brake system

Abstract

The fundamental approach of the present invention is to dispose bushes, in which pistons of a pumping apparatus for a vehicle brake system are movably disposed, in such a movable manner that they themselves may in dependence upon movements of the pistons act as pistons in order to supply brake fluid to the vehicle brake system. In particular, the bushes, whose pistons are pumping brake fluid into an associated brake circuit, do not act as pistons. On the other hand, brake fluid is fed back into a brake circuit by bushes, whose pistons are pumping substantially no brake fluid into the brake circuit but are taking in e.g. brake fluid removed from the vehicle brake system in order subsequently to pump it back into the brake circuit.

What is claimed is:  
     
       1. Pumping apparatus for a vehicle brake system, comprising 
       a housing,  
       bushes movably disposed in the housing, and  
       pistons movably disposed in the bushes, wherein the bushes are movable in dependence upon movements of the pistons,  
       characterized in that  
       the bushes cooperate in such a way that movements of one of the bushes in response to movements of the piston disposed therein give rise to movements of the other bushes.  
     
     
       2. Pumping apparatus according to  claim 1 , characterized in that the bushes are mechanically connected or integrated into a constructional unit. 
     
     
       3. Pumping apparatus according to  claim 1 , characterized in that the bushes have actuating members in order in dependence upon movements of the bushes to establish active connections between the latter. 
     
     
       4. Pumping apparatus according to  claim 1 , characterized in that the bushes act in the housing as a plunger piston. 
     
     
       5. Pumping apparatus according to  claim 1 , characterized in that 
       the bushes with the pistons disposed therein delimit in each case a pressure chamber, and  
       the bushes form in each case an outlet chamber in the housing.  
     
     
       6. Pumping apparatus according to  claim 5 , further including devices for establishing and interrupting fluid connections between the pressure chambers and associated outlet chambers in dependence upon movements of the pistons. 
     
     
       7. Pumping apparatus according to  claim 6 , characterized in that at least one of the outlet chambers acts as a pressure chamber for the bush, which forms said outlet chamber, when the fluid connection of said bush to the corresponding pressure chamber is interrupted. 
     
     
       8. Pumping apparatus according to  claim 7 , characterized in that the plunger piston acts as a piston in the at least one of the outlet chambers. 
     
     
       9. Pumping apparatus according to  claim 1 , further including restoring devices for the bushes. 
     
     
       10. Pumping apparatus according to  claim 1 , characterized in that the housing comprises two bushes, wherein the pistons of the latter operate with a phase displacement of 180°. 
     
     
       11. Pumping apparatus according to  claim 1 , characterized in that the housing comprises three bushes, wherein the pistons of the latter operate with a phase displacement of 120°. 
     
     
       12. Pumping apparatus according to  claim 5 , further including throttling devices associated with each bush for limiting the supply of brake fluid to the corresponding pressure chamber of the bush in dependence upon movements of the pistons. 
     
     
       13. Pumping apparatus according to  claim 12 , characterized in that the throttling devices limit the supply of brake fluid in dependence upon movements of the bushes. 
     
     
       14. Pumping apparatus according to  claim 13 , characterized in that the throttling devices throttle the supply of brake fluid when movements of the bushes exceed a defined range. 
     
     
       15. Pumping apparatus according to  claim 12 , characterized in that the throttling devices limit the supply of brake fluid to at least one of the pressure chambers, the piston of which having a higher pumping capacity compared to others of the pistons. 
     
     
       16. Pumping apparatus according to  claim 12 , characterized in that the throttling devices increase the supply of brake fluid to at least one of the pressure chambers, the piston of which having a lower pumping capacity compared to others of the pistons. 
     
     
       17. Pumping apparatus according to  claim 1 , characterized in that the pumping apparatus is a return pump for an antilock braking system. 
     
     
       18. Pumping apparatus according to  claim 1 , characterized in that the pumping apparatus is a brake fluid pump for the controlled build-up of braking forces in the vehicle brake system.